Hi ,
why havent you coupled both inputs , then each motor would have 1A instead of two motors have to share one output of the lb1836
i have done this a few times with the v1 ir receiver , it also has the lb1836
i also remove the ptc from the train motor and the electric fuse in the battery box or rechargeable unit , makes a huge difference in traction power especially at low speeds
the LB1836 has its own internal protection ;) one is more than enough